Selectivated metallosilicate catalyst composite for alkylaromatic conversion, process for the preparation thereof, and use thereof in hydrocarbon conversion

ABSTRACT

A repeated “soak and dry” selectivation process for preparing a modified metallosilicate catalyst composite is disclosed comprising of a mixture of amorphous silica, alumina and a pore size controlled metallosilicate useful for alkylaromatic conversion. The process comprises (a) contacting an intermediate pore metallosilicate with an organosilicon compound in a solvent for a specific duration and then recovering the solvent, (b) combining the organosilicon compound treated metallosilicate with water and then drying the catalyst, (c), repeating the steps a) and b) above and (d) calcining the catalyst in an oxygen containing atmosphere sufficient to remove the organic material and deposit siliceous matter on the metallosilicate. In a another embodiment, when the organosilicon compound is water soluble, step (b) may be avoided.

FIELD OF THE INVENTION

[0001] The present invention relates to a method of preparing themodified metallosilicate and a modified metallosilicate so prepared.This invention also relates to shape-selective hydrocarbon conversionprocesses using the modified metallosilicate catalyst prepared inaccordance with this invention.

BACKGROUND OF INVENTION

[0002] It is well known that dimethylbenzenes, i.e. xylenes has threeisomers, namely para-, meta- and ortho. The para-isomer is industriallymore important than that of the other two isomers.

[0003] 1,4-dimethylbenzene, i.e. para-xylene is useful in themanufacture of terephthalic acid that is an intermediate in themanufacture of polyester fibre. The production of para-xylene is a multimillion dollar business, and the large scale of the economies involvedmean that even a small improvement in these processes results inimproving the cost effectiveness of the process. Dimethylbenzenes, i.e.xylenes can be conveniently prepared by employing Friedel Craftsalkylation catalyst like AlCl₃, HCl, HF, BF₃ etc. However, thesecatalysts are corrosive in nature. In addition, it is impossible toavoid loss of raw material through multiple alkylations and other sidereactions. Further, the xylenes are produced in thermodynamicequilibrium composition, e.g. para-; meta-; ortho-=24:52:24. These threexylene isomers have very close boiling point to each other, the relativevolatility is nearly one. Hence separation of para-xylene is difficultand tremendously expensive.

[0004] Mobil Oil Corporation discovered a new type of zeolite known asZSM-5. The method of preparation of this zeolite is described in U.S.Pat. No. 3,702,886. The crystal structure of ZSM-5 zeolite has aspecific order of arrangement and is a porous aluminosilicate material.The specific pore size and regular channels have the capability toabsorb or allow entry of such molecules as are smaller in size than thatof the pore-opening, while rejecting larger molecules. Hence, it isfrequently referred as ‘molecular sieve’. In addition, ZSM-5 zeolitealso exhibits property of shape-selectivity. The phenomenon of shapeselectivity has been described in detail in “Shape-selective Catalysisin Industrial Application”, Vol.36, Mercel Dekker Inc. (1989).

[0005] There are many precedents in industry, which make use of thesecharacteristics to conduct chemical reactions. ZSM-5 catalyst ischaracterized by its selectivity, being able to satisfy the needs forhigh selectivity to products of different molecules, but its selectivityfalls short of expectation in respect of isomers of same kind ofproduct. For instance, when toluene is alkylated with methanol overZSM-5 catalyst, selectivity for xylenes is very high, but the ratio ofisomers of xylenes namely para-, meta- and ortho-, remains nearthermodynamic equilibrium composition. The details are reported in J. ofCatalysis, Vol.67, page 159 (1981), by W. W. Keading et. al.

[0006] Enhancement of para-selectivity, (the fraction of para-isomer ina mixture of para-disubstituted aromatics), by treatment withorganosilicon compound is usually referred to in the art asselectivation by silanation. The organosilicon compound is usually knownas selectivating agent. The method normally comprises contacting thezeolite with organosilicon compound, separation/removal of solvent (ifused), and calcination of zeolite to deposit silica or polymeric silicaas a layer on the zeolite.

[0007] It is known in the art that the efficiency of silica depositionin order to enhance the selectivity of the zeolite depends on the natureor the kind or the type or the molecular structure of the selectivatingagent, i.e. the organosilicon compound employed. The efficiency ofsilica deposition also depends on the temperature of silanation, thesolvents or the carrier for the organosilicon compound, the method orprocedure adopted for the selectivation. Pretreatment of the zeolite,i.e. treatment carried out before selectivating the zeolite has alsobeen found to affect the final selectivity of the zeolite. Alsopost-treatment, i.e. treatment after the selectivating the zeolite havealso been described in the art to further improve the selectivity of thezeolite for particular hydrocarbon conversion processes.

[0008] Selectivation of zeolites by silanation can be vapour phase orliquid phase. Liquid phase silanation is also referred as ex-situsilanation, or ex-situ selectivation. The zeolite is impregnated with anorganosilicon compound dissolved or dispersed in a carrier or solventfollowed by calcination of such treated zeolite in an oxygen containingatmosphere under conditions sufficient to remove organic materialtherefrom and deposit siliceous material on the zeolite. Such ex-situsilanation may result in deposition of at least 1% by weight ofsiliceous material on the catalyst or zeolite.

[0009] Examples of various patents, which teach the ex-situselectivation of zeolites to enhance para-selectivity are U.S. Pat. No.3,698,157 (to Allen et. al.), U.S. Pat. No. 4,002,697 (to Chen), U.S.Pat. Nos. 4,127,616 and 4,402,867 (both to Rodewald).

[0010] U.S. Pat. No. 3,698,157 (to Allen et al) describes improvedchromatographic separation of C₈ aromatic mixture for the recovery ofpara-xylene therefrom using aluminosilicate zeolite H-ZSM-5 modifiedwith octadecyltrichlorosilane.

[0011] U.S. Pat. No. 4,002,697 (to Chen) describes preparation ofcatalyst for xylene manufacture by toluene methylation. Silica modifiedcatalysts employed for the purpose were based on zeolites like ZSM-5,ZSM-11 or ZSM-21 of average crystal size of greater than 0.5μ, havingsurface deactivated by reaction with compounds of nitrogen or silicon,i.e. phenyl carbazole or dimethyldichlorosilane, (which are sufficientlylarge as to be unable to penetrate the pores of said crystallinealuminosilicate) followed by calcination. Pyridine was employed as asolvent for dimethyldichlorosilane.

[0012] U.S. Pat. No. 4,127,616 (to Rodewald) describes catalystssuitable for alkylation of toluene with methanol or ethanol, and toluenedisproportionation to obtain selectively the corresponding dialkylbenzene. The catalyst was prepared by deposition of large organosiliconcompound e.g. polymeric phenylmethyl silicone or polymericmethylhydrogen silicone on crystalline aluminosilicate H-ZSM-5, followedby calcination.

[0013] Silica modified zeolite catalysts have been described in U.S.Pat. No. 4,402,867 (to Rodewald), utilizing aqueous emulsion ofmethylhydrogen silicone. Such catalysts contain added amorphous silicawithin the interior of crystalline structure of the zeolite. Theorganosilicon compound employed in this patent is small enough to enterthe pores of the zeolite.

[0014] When the ex-situ selectivation process is repeated more thanonce, the procedure is referred to as multiple selectivation or multiplesilanation. In multiple selectivation method, the zeolite is treated atleast twice, generally from two to six times with a liquid mediumcontaining the organosilicon compound(s). In the multiple selectivationmethod, the zeolite is calcined after each impregnation of theorganosilicon compound. Examples of multiple silanation are found inU.S. Pat. No. 4,060,568 (to Rodewald), U.S. Pat. No. 4,283,306 and4,449,989 (both to Herkes), U.S. Pat. No. 5,349,114 (to Lago et.al),U.S. Pat. No. 5,495,059 (to Beck et.al), U.S. Pat. No. 5,552,357 (toLago et.al), U.S. Pat. No. 5,574,199 (to Beck et.al.), U.S. Pat. Nos.5,726,114 5,990,365 (to Chang et.al).

[0015] Modification of zeolites described in U.S. Pat. No. 4,060,568 (toRodewald), comprises preparing crystalline aluminosilicate zeolitecatalyst containing amorphous silica within the interior crystallinestructure of ZSM-5, by exposing the zeolite to a volatile silane ofsmall molecular dimension, which preferably enters the pores ofzeolites, followed by treatment with aqueous ammonia and calcination.The patent describes a catalyst modified by three such treatments withintermediate calcination after each treatment, but provides nodescription of any enhancement in catalytic selectivity or activity overthat which might follow from a single such treatment.

[0016] U.S. Pat. No. 4,283,306 and U.S. Pat. No. 4,449,989 (both toHerkes) also describe methods of modifying crystalline silica catalystby application of such silica sources as tetraethylorthosilicate (TEOS),or phenyl methyl silicone. Interestingly, performance of the catalysttreated once with a TEOS solution followed by calcination, was betterthan that of catalyst treated twice with TEOS, and calcined after eachtreatment. It showed that twice treated catalyst is less active and lessselective than the once treated catalyst as measured by methylation oftoluene by methanol, indicating that multiple ex-situ silanation confersno advantage over single silanation, rather results in a adverse effecton the para-dialkyl benzene selectivity.

[0017] U.S. Pat. No. 5,349,113 (to Chang et al) describes modificationof molecular sieve catalyst by treating with substantially aqueoussolution of a water soluble organosilicon compound. The method includesconcurrent preselectivation and activation to get activated catalyst.The invention also comprises in-situ selectivation by passing a highefficiency para-xylene selectivating agent along with the reactants.

[0018] U.S. Pat. No. 5,349,114 (to Lago et al) describes shape-selectivehydrocarbon conversion over modified catalytic molecular sieve, whichhas been modified by (i) being preselectivated with a first siliconcontaining compound and (ii) subsequently steamed at about 280° C. to400° C. The patent indicates that the molecular sieve is modified inas-synthesized conditions.

[0019] U.S. Pat. No. 5,495,059 (to Beck et al) also describes multipleex-situ selectivation sequence employing an aqueous carrier for theorganosilane compound. Each sequence includes an impregnation of themolecular sieve with the selectivating agent and a subsequentcalcination of the impregnated molecular sieve.

[0020] Selectivation of molecular sieves has been described duringextrusion by agglomerating with organosilicon compound by Chang et al inU.S. Pat. No. 5,541,146.

[0021] U.S. Pat. No. 5,552,357 (to Lago et al) describes catalystmodification by treatment of ZSM-5 in as-synthesised or in ion-exchangedform, first by treatment with a silicon containing polymer (propylaminesilane polymer) in substantially aqueous solution, followed bycalcination. The catalyst was further in-situ selectivated with a secondsilicon containing compound. For multiple ex-situ selectivation duringfirst stage, i.e. during treatment with propylamine silane polymer, thecatalyst was calcined after first treatment and before the secondtreatment.

[0022] Post-treatment of selectivated zeolite with a dealuminizingagent, e.g. monovalent or polyvalent acids, triethylene diamine, urea,ethylenediamine tetra acetic acid, ammonium hexafluorosilicate has beendescribed in U.S. Pat. No. 5,567,666 (to Beck et al).

[0023] U.S. Pat. No. 5,574,199 (to Beck et al) describes shape-selectivearomatization with a catalytic molecular sieve, which has been modifiedby multiple ex-situ selectivation method. The method involves exposingthe catalytic molecular sieve to at least two selection sequences, eachsequence comprising contacting the catalyst with dimethylphenylmethylpolysiloxane in a solvent, followed by calcination.

[0024] U.S. Pat. No. 5,726,114 (to Chang et al.) describes a method formodifying intermediate pore catalytic molecular sieve by multipleex-situ selectivation process by contacting the zeolite with an aqueousemulsion comprising of a silicon containing selectivating agentstabilized with the aid of surfactant and calcining the contactedmolecular sieve after each impregnation of silica. The method furthercomprises of mild steaming of the silica deposited zeolite and alsoin-situ trim selectivation of the ex-situ selectivated zeolite.

[0025] U.S. Pat. No. 5,990,365 describes a method for preparation of acatalyst comprising ZSM-5, rhenium and a selectivating agent e.g. eithercoke or siliceous material or a combination thereof. The multipleselectivation is carried out by (i) combining a bound form of zeolitewith an organosilicon compound (ii) calcining the organosiliconcontaining material to remove organic material therefrom to depositsiliceous material on the bound ZSM-5 and (iii) repeating steps (i) and(ii) at least once.

[0026] While the above mentioned art is of interest, there is nosuggestion of enhancing the selectivity of metallosilicate by treatmentwith aqueous water after the zeolite has been contacted withorganosilicon compound and before calcination of the zeolite to improvethe silanation efficiency. There is also no suggestion in any of theprior art known to the applicants of multiple silanation ofmetallosilicates without any intermediate calcination of organosiliconcompound treated zeolite after each silanation. Additionally, there isno suggestion of recycling the solvents/carriers for multiplesilanation.

[0027] Therefore, it would be a significant advance and improvement inthe art to overcome the difficulties, disadvantages and deficienciesassociated with conventional methods and procedures for modifyingcatalytic metallosilicates, molecular sieves modified by such methodsand the process of shape selective hydrocarbon conversion using suchmodified catalytic molecular sieves.

[0028] The present invention seeks to solves the difficulties,disadvantages, and deficiencies faced by the prior art by providing animproved method for modifying catalytic metallosilicate molecularsieves, and improved processes for shape selective hydrocarbonconversions.

OBJECTS OF THE INVENTION

[0029] Accordingly, it is an object of the invention to provide animproved method for silanation of metallosilicate for enhancing theshape-selectivity of the metallosilicate.

[0030] Yet another object of the invention is to provide an improvedcatalytic metallosilicate molecular sieve for shape selectivehydrocarbon conversion procedure.

[0031] Yet another object of the present invention is to provide animproved multiple silanation procedure and thereby to improve the easewith which the silanation of metallosilicate can be achieved as well asto reduce energy requirement and emission of such methods.

[0032] It is still another object of the present invention to improveshape selectivity in hydrocarbon conversion processes overmetallosilicates by providing metallosilicates having improved activityand selectivity, wherein the said metallosilicates have been modified bythe method described hereinafter.

SUMMARY OF THE INVENTION

[0033] The above and other objects are achieved by the novel process ofthe present invention referred to as “Repeated Soak and Dry, (RSD)”selectivation technique hereinafter. The invention is based on thefinding, inter alia, that treatment with aqueous water after themetallosilicate has been treated with organosilicon compound and beforecalcination, provides unexpectedly improved product, which in turnunexpectedly results in improved shape selective hydrocarbon conversion.

[0034] It has also been found that the “RSD” selectivation schemedescribed above provides unexpectedly better results for shape-selectivehydrocarbon conversion regardless of whether the process involves singlesilanation or multiple silanation modification procedure.

[0035] Furthermore, it has also been unexpectedly found that, thepresent improved multiple silanation scheme for modification ofmetallosilicate avoiding the intermediate calcination step after eachtreatment, results in excellent energy savings and lower emissions ofindustrial application. It also unexpectedly provides results for shapeselective hydrocarbon conversion, that are better or at least equivalentto those achieved by employing conventional modification method.

[0036] It is an important feature of the invention that it avoidsintermediate calcination steps after each silanation step and no priorart known to the applicants envisage multiple silanation process withoutalso envisaging intermediate calcinations after each silanation step.

[0037] Another important feature of the invention is combining theorganosilicon treated metallosilicate with water prior to calcination,especially, when the organosilicon employed is water-insoluble. Where awater soluble organosilicon compound is employed, it may not always benecessary to specifically combine the treated metallosilicate with watersince the zeolite extrudates, after the removal of solvent will normallybe wet due to the adherence of some water. However, where a solventother than water is used and after removal/separation (such asdecantation) of the solvent, there is no wetness in the zeoliteextrudate, it may be advantageous to add water and dry the product priorto calcination.

[0038] It is an important advantage of the present invention that in amultiple silanation procedure, the solvent employed for the firstsilanation can be recycled for the next silanation.

[0039] The present invention provides an improved method for modifyingcatalytic metallosilicate, the improved catalytic metallosilicatemolecular sieve and improved shape selective hydrocarbon processes overmodified metallosilicate molecular sieve.

[0040] In one aspect, the present invention includes a method forpreparing a modified metallosilicate molecular sieve catalyst composite,useful for hydrocarbon conversion to produce para-dialkylbenzene and thesaid method comprising steps of

[0041] a) contacting an intermediate pore metallosilicate with anorganosilicon compound in a solvent for a specific duration and thenremoving solvent.

[0042] b) combining the organosilicon compound containingmetallosilicate with water, and then drying the product.

[0043] c) repeating the steps a) and b) any number of times for multiplesilanation

[0044] d) calcining the product so obtained in an oxygen containingatmosphere under conditions sufficient to remove the organic material toobtain said modified metallosilicate molecular sieve catalyst composite.

[0045] Ideally, in this embodiment, the organosilicon compound employedis water insoluble.

[0046] The catalyst prepared according to the above method providesbetter results for shape selective hydrocarbon conversion. In anotherembodiment of the invention, the organosilane employed is water soluble,and therefore, step (b), i.e., combining with water may be dispensedwith.

[0047] Accordingly, the present invention also provides a method forpreparing a modified metallosilicate molecular sieve catalyst composite,useful for hydrocarbon conversion to produce para-dialkylbenzene and thesaid method comprising steps of

[0048] a) contacting an intermediate pore metallosilicate with a watersoluble organosilicon compound in a solvent for a specific duration andthen removing solvent.

[0049] b) drying the product so obtained.

[0050] c) repeating the steps a) and b) any number of times for multiplesilanation

[0051] d) calcining the product so obtained in an oxygen containingatmosphere under conditions sufficient to remove the organic material.

DETAILED DESCRIPTION OF THE INVENTION

[0052] The present invention relates to modified metallosilicatemolecular sieve catalyst composite, a method of preparation of themodified metallosilicate catalytic molecular sieve composite, and shapeselective hydrocarbon processes using the modified metallosilicatecomposite.

[0053] According to a preferred embodiment the modified metallosilicatemolecular sieve composite, comprises a mixture of amorphous silica, apore size regulated metalloaluminosilicate, preferably, aluminosilicateor galloaluminosilicate on an alumina or silica support. Thealuminosilicate or galloaluminosilicate is of pentasil family. Themethod for making aluminosilicates or zeolites of pentasil family isknown in the art. In the present invention, the modified aluminosilicateor galloaluminosilicate molecular sieve possesses a silica to aluminaratio of 70 to 700 and a silica to gallium oxides ratio of from 500 to5000. The catalyst composite may contain 20-80% of a suitable binder,selected from the group of silica, alumina, silica-alumina, alumina sol,silica sol, hydrated alumina etc. In a preferred embodiment the catalystcomposite contains 1 to 50% amorphous or polymeric silica or alumina ora mixture thereof.

[0054] The present invention will now be described with reference topreparation of a modified metallosilicate for e.g.,galloaluminosilicate, purely for the purposes of illustration. It is notthe intention of the applicants to exclude other metallosilicates andtherefore, references to galloaluminosilicate should be construedaccordingly in a wider sense.

[0055] The method of preparation of modified galloaluminosilicate ofpentasil family comprises (i) contacting the galloaluminosilicate withan organosilicon compound in a solvent and separating the solvent; (ii)optionally combining the organosilicon compound treatedgalloaluminosilicate with liquid water; (iii) drying the catalystcomposite; (iv) repeating steps (i) and (ii) for multiple silanation;and (v) calcining the catalyst under conditions sufficient to remove theorganic material and deposit siliceous material on the external surfaceof the galloaluminosilicate.

[0056] The metallosilicate employed herein are of pentasil family, e.g.ZSM-5, ZSM-11 or isomorphous substituted derivatives of those. Preferredmetallosilicates are Ga-Al-ZSM-5, Fe-Al-ZSM-5, Ga-ZSM-5, Fe-ZSM-5,Al-ZSM-5 and the like.

[0057] The metallosilicate may be employed in the form as-synthesised,or calcined Na-form or in active H-form. Preferred is the H-form of themetallosilicate. The galloaluminosilicate may be in unbound form or maybe in a bound form with a binder. The binder may be silica, alumina, orsilica alumina and the like. Preferred binder is either silica oralumina.

[0058] The organosilicon compound may be either a silicone or a silaneor a mixture thereof Examples of organosilicon compounds includephenylmethyl silicone, tetraethoxy silane, 3-aminopropyltriethyoxysilane etc. When a silane is chosen as a selectivating agent, thepreferred silanes are alkoxy silanes e.g. tetraethoxy silane, or3-aminopropyl triethoxy silane. It is also preferred that the kineticdiameter of the selected organosilicon compound is larger than the poresize opening of the metallosilicate which is subjected to modification.

[0059] The solvent in which the organosilicon compound is dissolved maybe any hydrocarbon liquid, e.g. aliphatic, alicyclic or aromatichydrocarbons, e.g. C₅-C₈ hydrocarbons, like pentane, hexane, heptane,octane, cyclopentane, cyclohexane, cycloheptane etc., and benzene,toluene, xylene, or alcohols like methanol, ethanol etc., or mixturethereof A preferred solvent is low boiling in nature as well asnon-polar and aprotic one. Water may also be employed when theorganosilicon compound is soluble in it. Preferred solvents arecyclohexane, toluene, mixture of toluene and methanol, water etc.

[0060] The concentration of the organosilicon compound in the solventmay be in the range of greater than 1 weight percent to less than 99weight percent, preferably greater than 2% to less than 50%, morepreferably, 5% to 25%. The organosilicon compound containing solution iscombined with the metallosilicate and treated at a temperature from 0°C. to the boiling point of the solvent for a duration of 0.1 to 24hours. It may be preferable to soak the metallosilicate in theselectivating solution, i.e. the organosilicon compound containingsolution for about 1 hour to 16 hours, or to reflux the combination ofmetallosilicate and the selectivating agent containing solution forabout 0.5 hour to about 12 hours. Subsequently, the solvent is separatedby any known means, e.g. by decantation, by filtration or bydistillation or by simply allowing for air drying at room temperatureand pressure. However, when an organic solvent is employed, it has beenfound convenient to separate the metallosilicate from the solution byeither filtration or distillation. It is preferred to separate themetallosilicate by distillation because such a procedure leaves themetallosilicate substantially free from the organic solvent. In the caseof other solvents like water etc, the metallosilicate may be recoveredby decantation or filtration.

[0061] In an embodiment of the present invention, the solvent employedfor dissolving the organosilicon compound is recycled from batch tobatch. For example, the solvent employed for silanation of one batch ofmetallosilicate catalyst, is recovered and reused for the silanation ofsecond batch of metallosilicate and so on. Such a procedure has theadvantage of minimizing the liquid effluent to zero level in acommercial unit producing such catalyst.

[0062] In another embodiment of the present invention, themetallosilicate is treated with liquid water subsequent to treatment ofthe metallosilicate with organosilicon compound. The procedure for thetreatment may be like addition of the metallosilicate to water orvice-versa. However, it has been found preferable and convenient to addwater to the organosilicon compound containing metallosilicate. Theamount of water added may be in the range of from 1 to 200 percent,preferably, 2% to 100% of the mass of the metallosilicate, morepreferably from 5% to 90% of the mass of metallosilicate, and mostpreferably, the volume of water added may be somewhat approximatelyequal to the interparticle volume of mass of the metallosilicate. Thewet extrudates are then dried at a temperature of 10 to 150° C.,preferably, 50° C.-150° C. for 1-24 hours, more preferably, at atemperature of 80° C.-130° C. for 2 - 20 hours.

[0063] It has been theorized that the alkoxysilanes, liketetraethoxysilane or 3-aminopropyltriethoxy silane which has a largerkinetic diameter than the pore openings of pentasil metallosilicates,cannot enter into the channels, and hence reacts only with acidiccentres which are located on the external surface of themetallosilicates. In a first step, the alkoxysilane molecule getsadsorbed and/or anchored on the external surface acidic sites. In asecond step, the reaction between the adsorbed alkoxysilane and theanchored alkoxysilane or between the anchored alkoxysilane moleculestakes place leaving out either dimethyl ether or ethyl alcohol. Thereaction may be considered as a sort of polymerization accompanied byhydrolysis. While not wishing to be limited by theory, it is believedthat the addition of water facilitates the hydrolysis of the anchoredalkoxysilane on the external surface of the metallosilicate. Thisincreases the efficiency of deposition of layered siliceous material,when the organosilicon compound containing metallosilicates are calcinedfor the above said purpose.

[0064] If a second selectivation, i.e. multiple silanation is nottargeted, the catalyst extrudates are then calcined in an oxygencontaining atmosphere, e.g. air, oxygen, or a mixture of nitrogen andoxygen etc. The temperature of the calcination may be in the range of160° C. to 800° C., preferably in the range of 300° C. to 600° C. andmost preferably, at 400° C. to 550° C. The calcination is done atatmospheric pressure for 2 to 20 hours, preferably, for 4 to 12 hours.

[0065] According to a preferred embodiment of the present invention, themultiple selectivation, i.e. the multiple treatments with theorganosilicon compound, are carried out without going for calcinationafter each selectivation. For example, the second treatment with theorganosilicon compound (the selectivating agent) is carried out byrepeating the procedures of steps (a), (b) and (c) as described above.The third treatment with the organosilicon compound is carried out byrepeating step (a), (b) and (c) above after second treatment. Thus,inventive process of modifying metallosilicate using multipleselectivation scheme as described hereinabove, avoids calcination aftereach selectivation and can be termed as “Repeated Soak and Dry” (RSD)selectivation method.

[0066] Such a process from the commercial point of view, is more energyefficient than that of the conventional procedure for modification ofzeolites through multiple silanation, wherein the zeolite is calcinedafter each treatment with the selectivating agent (i.e., theorganosilicon compound). In addition, the emissions released duringcalcinations are also reduced since the intermediate calcination stepsthemselves have been dispensed with.

[0067] While wishing not to be limited by any theory, it will beappreciated by those skilled in the art that repeated calcination ofmetallosilicates at high temperatures viz. in the range of more than500° C. for a long duration may be associated with some loss of the acidsites of the metallosilicates, including the acid sites located at theexternal surface. Therefore, the multiple silanation on such surfaces ofmetallosilicates might be less efficient, as compared to those wheresuch loss of acid sites has not taken place. Thus, the present method ofmultiple silanation without any intermediate calcination step has anadded advantage over the conventional procedure.

[0068] In another embodiment of the present invention envisagingmultiple treatment with organosilicon compound (i.e. the selectivatingagent), the organic solvent is recycled from the first treatment withselectivating agent. For example, during the second treatment withorganosilicon compound, the solvent recovered from the first treatmentis employed. Thus, there is no final liquid effluent in the whole methodof preparation of the modified metallosilicate catalyst composite.

[0069] Subsequent to the multiple selectivation of the metallosilicate(according the RSD selectivation method), the catalyst is finallycalcined in an oxygen containing atmosphere, e.g. air, oxygen, a mixtureof nitrogen and oxygen. The temperature of calcination may be in therange of 150° C. to 800° C., preferably, in the range of about 300° C.to 600° C. and most preferably, at about 400° C. to 550° C. The durationof calcination may be in the range of 2 to 10 hours preferably, 3 to 8hours, at atmospheric pressure.

[0070] The present invention also provides a process for shape-selectivehydrocarbon conversion, using the modified metallosilicate composite, asdescribed herein above. Such shape-selective reactions includedisproportionation or alkylation of mono alkyl benzene to selectivelyproduce para-dialkylbenzene, i.e. disproportionation of toluene tobenzene and a mixture of xylenes containing mostly para-xylene.Similarly, ethylbenzene may be disproportionated over the catalyst ofpresent invention to benzene and selectively para-diethylbenzene.Ethylbenzene can be ethylated using ethylene or ethanol topara-diethylbenzene employing the catalyst of the present invention.Toluene can be alkylated with methanol or ethylene or ethanol towardsselective formation of para-xylene or para-ethyl toluene. The presentcatalyst can also be employed for selective de-ethylation ofethylbenzene (i.e. converting ethylbenzene to benzene and ethylene) froma mixture of C₈ aromatics containing ethylene benzene and xylene.

[0071] As per the process conditions described in U.S. Pat. No.5,811,613 (to Bhat, Das and Halgeri), the entire content of which isincorporated herein by reference, the present catalyst may be employedfor catalyzing vapour phase ethylation of ethylbenzene to producepara-diethylbenzene, at a temperature of 523 K to 773 K, weight hourlyspace velocity 0 to 10 h⁻¹, in the absence of any carrier gas and usingsteam as co-feed. The process is under commercial operation in India.

[0072] As per the process conditions described in European Pat. No. EP0369078 (to Halgeri et. al.), the entire content of which isincorporated herein by reference, the present catalyst may be employedfor conversion of C₈ aromatic conversion, particularly for de-ethylationof ethylbenzene. The present catalyst may also be employed along withthe conventional C₈ aromatic isomerization catalyst for improvedperformance in terms of selective and enhanced ethylbenzene conversionof the isomerization feed.

[0073] The catalyst of the present invention, prepared by the RSDselectivation method described herein above is particularly useful forselective methylation of toluene to para-xylene. More particularly, thecatalyst under the methylation conditions is capable of providing hightoluene conversion per pass, while at the same time producing a veryhigh proportion of para-xylene among the total of the xylene isomers.However, it is to be understood that this catalyst may also be employedto catalyze other organic, especially hydrocarbon conversion reactions.

[0074] When the catalyst of the present invention is employed formethylation of toluene, the reaction conditions may include atemperature of about 350° C. to 650° C., a pressure of about atmosphericpressure to 30 atmospheres, a toluene to methanol mole ratio of about0.5:1 to 30:1, weight hourly space velocity 0.1-20 per hour, and ahydrogen or water or hydrogen and water as co-feed. The hydrogen orwater or hydrogen and water to total hydrocarbon ratio may be in therange of 0.1 to 10. The use of hydrogen or water or hydrogen and waterserves to suppress deactivation of catalyst, thereby increasing the lifeof catalyst.

[0075] The feedstocks for the present toluene methylation process, e.g.toluene and methanol are of commercial grade. Methanol employed for thepurpose may contain some water, e.g. 5-15%, or 5-35% or 5-50% water init, along with the usual commercial impurities in it. Toluene, mayoptionally contain some hydrocarbons, other than toluene. Suchhydrocarbons include benzene, xylenes, ethyltoluenes, and C₁₀ aromatics,as well as non-aromatics like paraffins and/or cycloparaffins.

[0076] It is to be understood that commercial toluene methylationprocess may run on a series of reactor wherein the effluent from thefirst reactor may be put to second reactor with additional input ofmethanol. Similarly, the effluent from the second reactor may be put tothe third reactor along with additional methanol. The amount ofremaining (unconverted) toluene from each reactor will depend on theconversion per pass and, accordingly, the concentration of toluene inthe feed will decrease from the first reactor to second, and second tothird etc. Thus the reactant feed may contain apart from toluene, atleast 1 percent to about 26 percent hydrocarbons comprising benzene,xylenes, ethyltoluenes, trimethylbenzenes and C₁₀ aromatics.

[0077] The invention will now be described in greater detail with thereference to the following examples, which are presented here for thepurpose of illustration only and should not be construed as limitativeof the scope of the present invention.

EXAMPLE 1 (Comparative)

[0078] 10 gm. of Ga-Al-ZSM-5 extrudates (containing 65% Ga-Al-ZSM-5 and35% alumina) in H- form were soaked in a solution containing 3.26 gmtetraethoxy silane in a mixture of 10 ml toluene and 6 ml methanol for 6hours at room temperature and pressure. The solvents (toluene andmethanol) were distilled off and the extrudates were dried in oven at120° C. overnight. Finally, the tetraethoxy silane treated extrudateswere calcined in a flow of air at 535° C. for 8 hours.

[0079] Catalytic performance of the modified Ga-Al-ZSM-5 catalystsamples was evaluated in a conventional continuous fixed bed down flow,integral reactor. Feed stream containing toluene and methanol waspreheated and put through the reactor using hydrogen/water as carriergas or hydrogen and water as co-feed. The products were analysed by GasChromatograph using capillary column. Reaction conditions and theresults are described in Table-1.

EXAMPLE 2

[0080] This example shows the effect of addition of liquid water inselectivation procedure. 10 gm of Ga-Al-ZSM-5 extrudates (containing 65%Ga-Al-ZSM-5 and 35% alumina) in H-form were added to a solution of 3.26gm of tetraethoxy silane in solvent mixture of 10 ml toluene and 6 mlmethanol at ambient conditions and allowed to soak for 6 hours. Theextrudates were recovered by distilling off the solvents. 5 ml of waterwas added to the extrudates and left for 30 minutes. The wet extrudateswere then dried at 120° C. for 12 hours, and calcined in the same way asdescribed in Example-1. The performance of the catalyst was evaluatedfor selective toluene methylation and the results are given in Table 1.TABLE 1 Catalyst performance for Toluene Methylation of Selectivatedmetallosilicates Temperature = 450° C., WHSV = 3.5 (based on toluene),Toluene: Methanol (mole) = 2, Toluene conversion Total Xylenespara-Xylene Example No wt %. wt %. selectivity 1 30.1 26.0 64.1 2 29.325.0 68.9

[0081] It can be seen that addition of liquid water after themetallosilicate has been treated with tetraethoxy silane, and beforecalcination, improves the para-xylene selectivity of the catalyst.

EXAMPLE 3 (Comparative)

[0082] This example is a comparative example for multiple silanation.The two silanations were carried out by repeating the whole procedure asdescribed in Example-1.

EXAMPLE 4

[0083] This example illustrates the improved multiple silanation methodof modification with addition of liquid water. The example is given fortwo silanations, but the technique holds for any number of silanations.The two silanations were carried out by repeating the complete procedureas described in Example-2. Performance of the catalysts of Example 3 andExample 4 are compared in Table 2. TABLE 2 Catalyst Performance forToluene Methylation of Selectivated metallosilicates Temperature = 450°C., WHSV = 3.5 (based on toluene), Toluene: Methanol (mole) = 2, TolueneConversion Total Xylenes Para-Xylene Example No wt %. wt %. selectivity3 26.8 23 77.2 4 25.8 22.4 85.1

[0084] Thus, it can be seen that multiple silanation with addition ofwater after the zeolite had been treated with tetraethoxy silanecompound and before calcination at each silanation step, markedlyimproves the para-xylene selectivity of the catalyst.

EXAMPLE 5

[0085] This example illustrates multiple silanation without anycalcination after each silanation and also without any water treatmentin each silanation step. The example is shown for two silanations butholds good for any number of silanations.

[0086] 10 gm of Ga-Al-ZSM-5 extrudates (containing 65% Ga-Al-ZSM-5 and35% alumina) in H- form were treated with tetraethoxy silane in atoluene-methanol mixture as given in Example-1. After removal of solventby distillation the extrudates were dried at 120° C. in an oven. Thedried extrudates were subjected to a second silanation following theprocedure just described. Finally, the extrudates were calcined at 535°C. for 8 hours. Performance of theses catalysts for toluene methylationis compared with that of Example 3, where the catalyst was preparedfollowing the conventional technique of calcination after eachsilanation (See Table 3). TABLE 3 Catalyst Performance for TolueneMethylation of Selectivated metallosilicates Temperature = 450° C., WHSV= 3.5 (based on toluene), Toluene: Methanol (mole) = 2, TolueneConversion Total Xylenes Para-Xylene Example No wt %. wt %. selectivity3 26.8 23 77.2 5 26.2 23.2 76.9

[0087] Thus, it can be seen that the modification of the metallosilicatethrough multiple silanation technique, without any intermediatecalcination after each selectivation provides equivalent results tothose where the same modification was carried out with calcination aftereach selectivation.

EXAMPLE 6

[0088] This example illustrates multiple silanation with water treatmentof the organosilicon compound treated metallosilicate and without anyintermediate calcination after each silanation step. The example isshown for two silanations but holds good for any number of silanations.

[0089] 10 gm of Ga-Al-ZSM-5 extrudates (containing 65% Ga-Al-ZSM-5 and35% alumina) in H-form were soaked for 6 hours in a solution containing3.26 gm tetraethoxy silane in 10 ml toluene and 6 ml methanol mixture.The solvent was then distilled off and the extrudates were recovered. 5ml water was added to the extrudates, left for a half an hour and thewet extrudates were dried in an oven at 120° C. The dried extrudateswere again treated with tetraethoxy silane and water and dried followingthe same procedure just described. Finally, the extrudates were calcinedat 535° C. for 8 hours. Performance of this catalyst for toluenemethylation is compared with that of the catalyst prepared in Example 4and given in Table 4.

EXAMPLE 7

[0090] This example illustrates the reuse of solvents employed fordissolving the organosilicon compound. The procedure followed for thepreparation of the catalyst was same as described in Example 6 exceptthat the solvent recovered by distillation during first stage silanationwas employed for the second stage silanation. Performance of thecatalyst thus prepared is included in Table 4. TABLE 4 CatalystPerformance for Toluene Methylation of Selectivated metallosilicatesTemperature = 450° C., WHSV = 3.5 (based on toluene), Toluene: Methanol(mole) = 2, Toluene Conversion Total Xylenes Para-Xylene Example No wt%. wt %. selectivity 4 25.8 22.4 85.1 6 26 22.6 84.6 7 26.1 22.5 84.8

[0091] Thus, it can be seen that the modification of the metallosilicatethrough multiple silanation technique with addition of water after themetallosilicate had been treated with organosilicon compound and withoutany intermediate calcination after each selectivation providesequivalent results to those where the same modification was carried outwith calcination after each selectivation. Also the repeated use of therecovered solvent does not affect the performance of the catalyst.

EXAMPLE 8 (Comparative)

[0092] This example illustrates the preparation of catalyst by multiplesilanation with calcination after each silanation employing a watersoluble organosilicon compound, e.g., 3-aminopropyltriethoxy silane asselectivating agent.

[0093] 10 gm of galloaluminosilicate extrudates (containing 65%Ga-Al-ZSM-5 and 35% alumina) in H-form were soaked in a solutioncontaining 3.3 g of 3-aminopropyltriethoxy silane in 6.8 gm of water forsix hours. The supernatant liquid was then decanted off and the wetextrudates were then dried at 120° C., and calcined in a flow of air at535° C. for 20 hours. By repeating the procedure again, the secondsilanation was completed. Performance of the catalyst for toluenemethylation was evaluated and given in Table 5.

EXAMPLE 9

[0094] This example shows the benefit of avoiding the intermediatecalcination steps for multiple silanation employing3-aminopropyltriethoxy silane as selectivating agent.

[0095] 10 gm of galloaluminosilicate extrudates (containing 65%Ga-Al-ZSM-5 and 35% alumina) in H-form were soaked in a solutioncontaining 3.4 gm of 3-aminopropyltriethoxy silane in 6.8 g of water forsix hours. The supernatant liquid was then decanted off and the wetextrudates were then dried at 120° C. By repeating the procedure again,the second silanation was completed. Finally, the treatedgalloaluminosilicate extrudates were calcined in a flow of air at 535°C. for 20 hours. The performance of the catalysts was evaluated forselective toluene methylation and the results are given in Table 5.TABLE 5 Catalyst performance for Toluene Methylation of Selectivatedmetallosilicates Temperature = 450° C., WHSV = 3.5 (based on toluene),Toluene: Methanol (mole) = 2, Toluene Conversion Total XylenesPara-Xylene Example No wt %. wt %. selectivity 8 25.3 21.8 73.5 9 26.021.7 74.0

EXAMPLE 10 (Comparative)

[0096] 10 gm of aluminosilicate extrudates (containing 65% Ga-Al-ZSM-5and 35% alumina) in H-form were soaked in a solution containing 0.72 gmof 3-aminopropyltriethoxy silane in 6 ml water for six hours. Thesupernatant liquid was then decanted off and the wet extrudates werethen dried at 120° C. The dried extrudates were calcined in a flow ofair at 535° C. for 8 hours. The calcined extrudates were again soaked ina in a solution containing 0.72 gm of 3-aminopropyltriethoxy silane in 6ml water for six hours. After removing the excess liquid, the extrudateswere dried at 120° C. Finally, the extrudates were again calcined in aflow of air at 535° C. for 8 hours The performance of the catalysts ofExample 10 was evaluated for selective toluene methylation and theresults are given in Table 6.

EXAMPLE 11

[0097] This example shows the benefit of avoiding the intermediatecalcination steps for multiple silanation employing3-aminopropyltriethoxy silane as selectivating agent. The example isgiven for two silanations but the technique holds for any number ofsilanations.

[0098] 10 gm of aluminosilicate extrudates (containing 65% Ga-Al-ZSM-5and 35% alumina) in H- form were soaked in a solution containing 0.72 gmof 3-aminopropyltriethoxy silane in 6 ml water for six hours. Thesupernatant liquid was then decanted off and the wet extrudates werethen dried at 120° C. The dried extrudates were again soaked in asolution containing 0.72 gm of 3-aminopropyltriethoxy silane in 6 mlwater for six hours. After removing the excess liquid, the extrudateswere dried at 120° C. Finally, the extrudates were calcined in a flow ofair at 535° C. for 8 hours. The performance of the catalysts wasevaluated for selective toluene methylation and compared with those ofthe catalyst prepared in Example 10. The results are given in Table 6.TABLE 6 Catalyst performance for Toluene Methylation of Selectivatedmetallosilicates Temperature = 450° C., WHSV = 3.5 (based on toluene),Toluene: Methanol (mole) = 2, Toluene Conversion Total XylenesPara-Xylene Example No wt %. wt %. selectivity 10 26.2 23.1 80.5 11 26.123.2 80.8

[0099] Obviously, many modifications and variations of the presentinvention are possible in the light of above teaching. For example, itis obviously possible in the light of the above description and teachingto prepare a modified metallosilicate catalyst composite by theinventive “RSD” method of making the same as described hereinbefore, soas to achieve para-xylene selectivity as high as more than c.a. 90%, orsay 95%, or say more than 99%, while maintaining a reasonably acceptabletoluene conversion level. It is, therefore, to be understood that withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically described.

1. A process for preparing a modified metallosilicate catalyst compositecomprising of a mixture of amorphous silica, alumina and a pore sizecontrolled metallosilicate useful for alkylaromatic conversion, the saidprocess comprising a) contacting an intermediate pore metallosilicatewith an organosilicon compound in a solvent for a specific duration andthen recovering the solvent b) combining the organosilicon compoundtreated metallosilicate with water and then drying the catalyst c)repeating the steps a) and b) above d) calcining the catalyst in anoxygen containing atmosphere sufficient to remove the organic materialand deposit siliceous matter on the metallosilicate.
 2. A process asclaimed in claim 1 wherein said organosilicon compound is waterinsoluble.
 3. A process as claimed in claim 2 wherein the saidorganosilicon compound is tetraalkoxy silane.
 4. A process as claimed inclaim 3 wherein the said tetraalkoxy silane is tetraethoxy silane.
 5. Aprocess as claimed in claim 1 wherein the said solvent is selected fromlower aliphatic alcohols, C₅-C₁₀ saturated linear or cyclichydrocarbons, C₆-C₈ aromatics or mixture thereof.
 6. A process asclaimed in claim 5 wherein the said solvent is a mixture of toluene andmethanol.
 7. A process as claimed in claim 1 wherein the concentrationof the organosilicon compound in said solvent is in the range of 1 to 25percent by weight.
 8. A process as claimed in claim 1 wherein the saidmetallosilicate is treated with the organosilicon compound containingsolution for 0.5 to 24 hours.
 9. A process as claimed in claim 1 whereinthe said solvent is recovered after metallosilicate is treated with theorganosilicon compound containing solution.
 10. A process as claimed inclaim 1 wherein amount of said water is in the range of from 1 to 200percent, preferably 2 to 100%, more preferably, 5 to 90% of the mass ofthe metallosilicate.
 11. A process as claimed in claim 1 wherein thesaid water combined metallosilicate composite is dried at a temperatureof from 10 to 150° C.,
 12. A process as claimed in claim 11 wherein thesaid water combined metallosilicate composite is dried at a temperatureof 50 to 150° C.
 13. A process as claimed in claim 11 wherein the saidwater combined metallosilicate composite is dried at a temperature offrom 80 to 130° C.
 14. A process as claimed in any of the claims 11wherein the said wet metallosilicate composite is dried for from 1 to 20hours.
 15. A process as claimed in claim 1 wherein the step a) and stepb) are repeated more than once.
 16. A process as claimed in claim 1wherein the solvent recovered is reused.
 17. A process as claimed claim1 wherein the said calcination is carried out at a temperature in therange of from 160 to 800° C.
 18. A process as claimed claim 17 whereinthe said calcination is carried out at a temperature in the range offrom 300 to 600° C.
 19. A process as claimed claim 17 wherein the saidcalcination is carried out at a temperature in the range of from 400 to550° C.
 20. A modified metallosilicate catalyst composite comprising ofa mixture of amorphous silica, alumina and a pore size controlledmetallosilicate, useful for alkylaromatic conversion prepared by theprocess of claim
 1. 21. A process for preparing a modifiedmetallosilicate catalyst composite comprising of a mixture of amorphoussilica, alumina and a pore size controlled metallosilicate useful foralkylaromatic conversion, the said process comprising a) contacting anintermediate pore metallosilicate with a water insoluble organosiliconcompound in a solvent and then recovering the solvent b) combining theorganosilicon compound treated metallosilicate with water, the amount ofwater employed being in the range of from 1 to 200 percent of the massof said metallosilicate, c) drying the product from step b) at atemperature in the range of 10 to 150° C.; d) repeating the steps a) andb) above e) calcining the product in an oxygen containing atmosphere ata temeprature in the range of 160 to 800° C. sufficient to remove theorganic material and deposit siliceous matter on the metallosilicate.22. A process for preparing a catalyst composite comprising of a mixtureof amorphous silica, alumina and a pore size controlled metallosilicateuseful for alkylaromatic conversion, said process comprising a)contacting an intermediate pore metallosilicate with an organosiliconcompound in a solvent for a specific duration and then recovering thesolvent b) drying the catalyst c) repeating the steps a) and b) above d)calcining the catalyst in an oxygen containing atmosphere sufficient toremove the organic material and deposit siliceous matter on themetallosilicate.
 23. A process as claimed in claim 22, wherein saidorganosilicon compound used is water soluble.
 24. A process as claimedin claim 22 wherein the said organosilicon compound isaminoalkytrialkoxy silane.
 25. A process as claimed in claim 24 whereinthe said aminoalkytrialkoxy silane is 3-aminpropyl triethoxysilane. 26.A process as claimed in claim 22 wherein the said solvent is selectedfrom lower aliphatic alcohols, C₅-C₁₀ saturated linear or cyclichydrocarbons, C₆-C₈ aromatics or mixture thereof and water.
 27. Aprocess as claimed in claim 22 wherein the said solvent is water.
 28. Aprocess as claimed in claim 22 wherein the concentration of theorganosilicon compound in said solvent is in the range of 1 to 99%,preferably, 2 to 50%, more preferably 5 to 25% by weight.
 29. A processas claimed in claim 22 wherein the said metallosilicate is treated withthe organosilicon compound containing solution for 0.5 to 24 hours. 30.A process as claimed in claim 22 wherein the said solvent is recoveredafter metallosilicate is treated with the organosilicon compoundcontaining solution.
 31. A process as claimed claim 22 wherein the saidorganosilicon compound treated metallosilicate composite is dried at atemperature form 10 to 150° C.
 32. A process as claimed in claim 22wherein said water treated metallosilicate composite is dried for atleast 1 hour.
 33. A process as claimed in claim 22 wherein the step a)and step b) are repeated at least once.
 34. A process as claimed inclaim 22 wherein the solvent recovered from the silanation step isreused for further silanation.
 35. A process as claimed in claim 22wherein the said calcination in said oxygen containing atmosphere iscarried out at a temperature in the range 160 to 800° C.
 36. A processas claimed in claim 22 wherein the said metallosilicate is selected fromthe group of pentasil familiy e.g. such as Ga-ZSM-5, Fe-ZSM-5, B-ZSM-5,Ga-Al-ZSM-5, Fe-Al-ZSM-5, B-Al-ZSM-5.
 37. A process as claimed in claim22 wherein the said metallosilicate is selected from the group ofpentasil familiy e.g. such as Ga-ZSM-5, Fe-ZSM-5, B-ZSM-5, Ga-Al-ZSM-5,Fe-Al-ZSM-5, B-Al-ZSM-5.
 38. A process as claimed in claim 36 whereinsaid metallosilicate is Ga-Al-ZSM-5 having silicon to aluminium ratio inthe range of 150 to 600 and silicon to gallium ratio is in the range of500 to
 2000. 39. A process as claimed in claim 37 wherein saidmetallosilicate is Ga-Al-ZSM-5 having silicon to aluminium ratio in therange of 150 to 600 and silicon to gallium ratio is in the range of 500to
 2000. 40. A process for alkylaromatic hydrocarbon conversioncomprising contacting the a mixture of hydrocarbons feed with a catalystunder the conditions effective to convert said hydrocarbon feed to ahydrocarbon product different from said hydrocarbon feed, wherein saidcatalyst is prepared by a process comprising a) contacting anintermediate pore metallosilicate with an organosilicon compound in asolvent for a specific duration and then recovering the solvent b)combining the organosilicon compound treated metallosilicate with waterand then drying the catalyst c) repeating the steps a) and b) above d)calcining the catalyst in an oxygen containing atmposphere sufficient toremove the organic material and deposit siliceous matter on themetallosilicate.
 41. A process for alkylaromatic hydrocarbon conversioncomprising contacting the a mixture of hydrocarbons feed with a catalystunder the conditions effective to convert said hydrocarbon feed to ahydrocarbon product different from said hydrocarbon feed, the whereinsaid catalyst is prepared by the process comprising a) contacting anintermediate pore metallosilicate with an organosilicon compound in asolvent for a specific duration and then recovering the solvent b)drying the catalyst c) repeating the steps a) and b) above d) calciningthe catalyst in an oxygen containing atmposphere sufficient to removethe organic material and deposit siliceous matter on themetallosilicate.
 42. A process as claimed in claim 40 wherein thehydrocarbon conversion is selective alkylaromatic alkylation of with analkylating agent selected form the lower aliphatic alcohol or loweralkenes.
 43. A process as claimed in claim 42, wherein the alkylaromaticcompound is toluene.
 44. A process as claimed in claim 40, wherein thealkylating agent is methanol.
 45. A process as claimed in claim 40wherein the product comprises of xylenes with very high selectivity forpara-xylene and the said conversion is by alkylation.
 46. A process asclaimed in claim 40 wherein the hydrocarbon conversion is selectivealkylaromatic alkylation of with an alkylating agent selected form thelower aliphatic alcohol or lower alkenes.
 47. A process as claimed inclaim 42, wherein the alkylaromatic is toluene.
 48. A process as claimedin claim 40, wherein the alkylating agent is methanol.
 49. A process asclaimed in claim 40 wherein the product comprises of xylenes with veryhigh selectivity for para-xylene and the said conversion is byalkylation
 50. A process for preparing a modified metallosilicatecatalyst composite comprising of a mixture of amorphous silica, aluminaand a pore size controlled metallosilicate useful for alkylaromaticconversion, the said process comprising a) contacting an intermediatepore metallosilicate with a water soluble organosilicon compound in asolvent and then recovering the solvent b) drying the product from stepa) at a temperature in the range of 10 to 150° C.; c) repeating thesteps a) and b) above d) calcining the product in an oxygen containingatmosphere at a temeprature in the range of 160 to 800° C. sufficient toremove the organic material and deposit siliceous matter on themetallosilicate.